(1) Monte Alban, a major archaeological site located on the top of high ridge overlooking the modern city of Oaxaca. It was occupied between 500BC and 850AD and dominated the Oaxaca region.
(2) Mitla, a smaller site occupied at least since the Classic period (100-650 AD). It developed into a major ceremonial center beginning c. 850 AD. It was still occupied when the region was conquered by the Spanish in the 1520s.
(3) The Church and former monastery of Santo Domingo de Guzmán. It is a Baroque ecclesiastical complex in the city of Oaxaca that was constructed beginning in 1561. The complex includes the church as well as an extensive system of courtyards, cloisters and rooms that were used as a monastery. The former monastery now houses the Cultural Center of Oaxaca, which was founded with the help of Oaxaca-born artist Francisco Toledo. This museum includes an important collection of Pre-Spanish artifacts from Monte Alban and other sites in the region as well as many artifacts from the early Spanish period. (Wikipedia)
(4) Other historic structures in Oaxaca and surrounding region
All of the structures seen today at Monte Alban and Mitla have been significantly reconstructed.